VULCAN VGP Series catalyst can selectively hydrogenate acetylene and other impurities in refinery off gases to allow for recovery of valuable olefins. The catalyst removes acetylene, oxygen, arsine and phosphine at typical operating temperatures of 150-260°C through hydrogenation and chemisorption reactions. The performance of the catalyst gradually declines due to fouling and requires periodic regeneration by heating in air and steam to remove carbon deposits.

1. C2PT Catalyst Process Technology
By Gerard B Hawkins
Managing Director
FCC Off Gas Treatment

2.  Refinery off gas sourced from a number of units
 FCC / Coker / HDT / etc
 FCC off gas contains valuable olefins which can be recovered by
stand-alone cryogenic unit
 Gas stream typically contains many contaminants which affect
either final product specs or processing options

3.  H2S Catalyst poison
 COS Impacts on C3= product spec
 RSH Impacts on C2= / C3= product spec
 Acetylene Impacts on C2= / C3= product spec
 Oxygen Impacts on C2= / C3= product spec
 Chlorides Corrosive to aluminium
 Ammonia Potential reactant to form NH4NO3
 Nitric oxides Can react to form explosive nitroso gums
 Mercury Attacks aluminium in cold section
 Arsine Impacts C3= product spec
 HCN Impacts C2= / C3= product spec
 H2O Freezes in cold section

4.  H2S Amine/caustic wash + absorbent guard bed
 COS Hydrolysis or solid bed absorption
 RSH Caustic and/or solid bed absorption
 Acetylene Hydrogenation to ethylene across catalyst
 Oxygen Hydrogenation to water across catalyst
 Chlorides Solid bed absorbent
 Nitric oxides Hydrogenation to NH3 across catalyst
 Mercury Solid bed absorbent
 Arsine Solid bed absorbent
 HCN Solid bed absorbent or hydrogenation across
catalyst
 H2O Regenerable mol sieve

5. Products for sale
as polymer feeds
and LPG
Feed Gas
Compression
Acetylene
conversion
Acid Gas
Removal
Contaminant
Absorption
Steps
Drying
Cryogenic
Recovery
Unit
Product
Fractionation
Off gas to fuel or
hydrogen recovery
Refinery off gas
streams
Typical Off Gas Processing Scheme

6.  Supply of the full range of catalysts / absorbents
 for off gas processing
 and / or treatment of fractionated product streams
 Commercial references for both duties under the
product brand name VULCAN VGP Series
 Input to the flow sheet and reactor design
 All spent catalysts / absorbents can be reprocessed

7.  Amine and caustic systems most cost effective route
for bulk H2S removal
 For specifications of < 3 ppmv H2S then a fixed bed absorbent
bed on polishing duty most cost effective
 Polishing guard bed also provides insurance for amine or caustic
unit upsets
 VULCAN VGP Series H2S absorbents market leader in gas processing
industry and wide-spread use in refineries to protect catalysts from sulfur
poisoning

8.  Amine & caustic systems not effective at COS removal
 COS can be hydrolysed across a catalyst
COS + H2O -----> H2S + CO2
or absorbed directly by reaction with a non-regenerable
absorbent bed
 Performance of the catalyst dependant on component partial
pressures and temperature
 VULCAN Absorbent references on reducing off-gas streams and
polymer grade propylene streams

9.  Amine systems not effective at RSH removal
 Caustic will remove RSH but struggles to meet tight exit
specifications
 VULCAN Series absorbents remove RSH onto a non-
regenerable absorbent at ambient temperature
 VULCAN Series RSH absorbents in use on refineries to protect
catalysts from sulfur poisoning and meet product specifications

10.  Sulfided metal catalyst removes all
 acetylene hydrogenated to ethylene
 oxygen hydrogenated to water
 arsine, phosphine and cyanides absorbed
 nitriles converted to amines
 cyanides converted to ammonia
 Key to activity is proprietary catalyst sulfiding procedure
 VULCAN Series catalyst proven for selective hydrogenation duties
on both refineries & petrochemical plants

11.  HCl removed by chemical reaction onto a non-
regenerable absorbent bed
 Care needed if Aluminas specified because of danger of synthesis
of organic chlorides which are difficult to remove
R= + HCl ------> RCl
This does not occur with VULCAN Series absorbents
 VULCAN Series absorbents market leader in refineries for catalytic
reformer off gas dechlorination

12.  NO and NO2 hydrogenated across a catalyst
NOx + H2 -----> NH3 + H2O
 Key is to ensure no co-hydrogenation of olefins
 Proven on side-stream reactor unit on commercial FCC unit

13.  Mercury reacts with absorbent to form mercuric
sulfide which remains as part of absorbent structure
 Exit mercury specification determined by equilibrium
 Typical exit specs < 0.001 ppb
 VULCAN VGP Series mercury absorbents proven in
many gas processing plants to meet transmission
specifications and protect aluminium equipment

14. The primary objective of the oxygen converter
is to reduce the Oxygen content of the treated
gas to less than 0.1 ppm (V)
Acetylene < 1 ppm (wt)
Arsine < 5 ppb (wt)
Phosphines < 5 ppb (wt)

15. Cost effectiveness:
VULCAN VGP Series catalyst must meet several criteria.
• Meet Oxygen specification of less than 0.1 vppm
• Meet Acetylene specification of less than 0.1 wppm
• Meet Arsine specification of less than 5 vppb
• Meet Phosphine specification of less than 5 vppb
Provide a 18 month cycle length.

16. Client minimum guarantee levels for the following
performance metrics at SOR:
• Oxygen content of treated gas to be less than 0.1
ppmv at maximum treat gas rate.
• Acetylene specification of less than 0.1 wppm at
maximum treat gas rate.
• Arsine specification of less than 5 vppb at
maximum treat gas rate.
• Phosphine specification of less than 5 vppb
at maximum treat gas rate.

17. Catalysts promote chemical reactions
and accelerate the rate at which a
chemical reaction approaches
equilibrium.
The catalyst provides a suitable surface for reactants to
adsorb and for products to desorbed.
Primary Function - to lower the activation energy of the
reaction by providing a suitable reaction pathway.

18. GBHE offers VULCAN VGP Series catalyst for the treatment of
fluidized catalytic cracker unit (FCCU) off gas to remove a variety of
impurities, which are unacceptable for downstream processing in
which useful olefins are recovered in a cold train.
 Acetylene and higher acetylenes are hydrogenated selectively by
VULCAN VGP Series catalyst using the large excess of hydrogen in
the process stream without significant onward hydrogenation of the
olefins, which are to be recovered.
 Oxygen is removed by hydrogenation to H2O.
 Traces of Phosphine and arsine are removed by chemisorption.

19. CATALYST DESCRIPTION
Form Spheres
 Size nominal 8 mm
TYPICAL CHEMICAL COMPOSITION
Component Wt. % dry
Ni 0.5%
Co 0.15%
Cr 0.05%
Al2O3 84 – 89%
PHYSICAL DESCRIPTION
Crush Strength > 50 Kgs
Bulk Density 1 – 1.1 Kg/L

20.  VULCAN VGP Series: Catalyst of the sulfided Ni type.
 The catalyst is principally designed to hydrogenate
acetylene to ethylene by the reaction:
C2H2 + H2  C2H4

21. Typical Feed Impurity Levels
◦ Inlet acetylene 1000 - 3000 ppm mol
◦ Outlet acetylene < 1 ppm mol
The VULCAN VGP hydrogenates other acetylene and diene
compounds in FCCU off gas.
(MA/PD) Removal efficiency 60 - 80 %
(BD) Removal efficiency 20 - 30 %

22. O2 Oxygen is removed by the reaction:
O2 + 2 H2  2 H2O
Typical oxygen Levels:
◦ Inlet oxygen 300 - 1000 ppm mol
◦ Outlet oxygen < 1 ppm mol can be achieved
Optimum Inlet temperature range: 190 – 200 oC.

23. Operating temperature range: 150 – 260 oC (300 – 500 oF).
◦ Delta T: The temperature rise is typically 30 – 50 oC
 Dependent on the amount of acetylenes, dienes and oxygen in the feed
 The catalyst selectivity
◦ Activity for the desired hydrogenation reactions and selectivity for
olefin hydrogenation is controlled by;
 Continuous sulfur doping with H2S
 Operating temperature
Both of which must be varied as the catalyst ages.

24. ◦ A new charge of catalyst requires sulfiding prior to being
brought on line, and after periodic steam/air regenerations.
◦ The reactions take place in the presence of a large excess of
hydrogen over acetylene
 Typically 5 - 10 mol % and 2000 ppm mol (respectively)
◦ High selectivity and minimizes undesirable hydrogenation
 ethylene and propylene products.

25. The catalyst performance slowly deteriorates
over time online due to the build up of
foulants on the catalyst surface.
Once the selectivity and activity of VULCAN VGP become
unacceptable, the catalyst requires regeneration.
◦ The regeneration frequency depends on the operating
conditions, the catalyst age, vessel sizing and the level of
acetylene slip or ethylene loss that the operator can tolerate.
◦ Regenerations are usually required every few months but may be
more or less frequent.

26. ◦ Regeneration conditions require heating of the catalyst in
air/steam at approximately 500 oC for approximately one week
until the fouling species are removed.
◦ Re-sulfiding before the catalyst is ready for re-use
◦ VULCAN VGP operates in a sulfided form, which has activity
for the absorption of various species
 Phosphine
 Arsine.

27. NiO is a known catalyst for the reduction
of NOx with both CO and H2, at temperatures below 392
0F (200 0C), with the principal product of reaction
being N20.
NO and NO2 hydrogenated across a catalyst
NOx + H2 -----> NH3 + H2O
References:
E Echigoya et al, Bull. Japan. Petr. Inst, 1975, 17, 232
G V Glazneva et al., Dokl. Akad. Nauk. SSR, 1973, 213, 971
T P Kobylinski et al., J. Catal, 1973, 31, 450
F Nozaki et al, Bull. Chem. Soc. Japan. 1975, 48, 2764

28. Control parameters:
A combination of rate of sulfur injection and inlet temperature
optimization
Higher temperature increases activity but diminishes
selectivity so that the acetylene conversion is increased but
also the level of ethylene hydrogenation increases
Oxygen conversion can be affected also
Conversely, higher sulphur decreases activity but augments
selectivity

29. There are numerous factors which affect the catalyst
performance:
- Hydrogen partial pressure:
Increases hydrogenation activity and therefore lower
selectivity
Sulfur (ppm):
Any sulfur injection must be adjusted to
compensate for varying levels
of feed sulfur
- Moisture:
Increasing H2O diminishes activity

30. • - CO level:
Increasing CO decreases activity and helps selectivity
but large changes are needed for the effect to be
significant;
• - Space velocity:
Faster gas flow results in less apparent
activity but more selectivity;
• - Olefin partial pressure:
In theory the selectivity will decrease with increasing
olefin levels but the effect is small.

31. • Typically inlet temperature
200 oC (392 oF)
Reaction may be substantial at 190 oC (374 oF) or may require
an increase in temperature to 220 oC (428 oF)
Typical Sulfur levels: 2 - 50 ppmv (total sulphur)
Over the lifecycle, temperatures should be increased and
sulfur injection rates reduced, in order to maintain catalyst
activity. - Decreased selectivity
Under certain conditions, the catalyst will desulfide to give Ni
rather than NiS and this is an effective ethylene hydrogenation
catalyst so selectivity may collapse.

32. Permanent Poisons
Arsenic, lead, mercury, cadmium
 Silica, Iron Oxide….
Temporary Poisons
Sulfur, carbon

33. - Heavy metals in FCC feedstocks
• Nickel
• Vanadium
- Tramp iron contamination, formed as corrosion
products within the pipe work
- Scale and carbon deposits from heaters and
exchangers
- Polymerization caused by reactive molecules
within the feedstock
- Particulates contained within the feedstock or
caused by upstream attrition of catalysts.

34. 0
0.01
0.02
0.03
0.04
0.05
0.06
0.001 0.01 0.1 1 10 100 1000
Pore size (microns)
Cumulativevol(mls/g)
Catalyst A
Catalyst B
The contaminants may vary in size from sub micron to several
hundred microns and be deposited in the interstitial voids
between the catalyst spheres.
Result: Flow restriction, channeling, and a reduction in catalyst
activity by;
- Deposition and encapsulation of the catalyst
surface
- Pore mouth narrowing
mechanism leading to
eventual total pore
plugging

35. During operation, carbonaceous polymer builds up on the
catalyst surface for side reactions of unsaturated
hydrocarbons in the process gas. As a result, catalyst
selectivity and activity declines.
VULCAN VGP can be regenerated using a steam/air oxidation
at high temperature to remove the carbonaceous polymer
deposits.
The regeneration frequency depends on the operating
conditions, the catalyst age, vessel sizing and the level of
acetylene slip or ethylene loss that the operator can tolerate.

36. V5
V2
V4
FeedGAS
V1
BA
V6
V3
PRODUCT
GAS
Regeneration conditions
require heating of the
catalyst in air/steam at
approximately 500 oC for
until the fouling species
are removed.

37.  VULCAN VGP is formulated to hydrogenate acetylene to
ethylene. Other diene compounds can also be hydrogenated
with relatively high efficiency, and impurities removed by
chemisorption
 The amount of temperature rise will vary depending on the inlet
impurity content and catalyst selectivity
 Continuous sulfur injection is required to maintain catalyst
selectivity
 VULCAN VGP is regenerable